PROJECT SUMMARY Inhalation exposures of metal-based particles have been associated with severe adverse health outcomes from metal fume fever to cancer. Compared to the larger particles present in samples collected with typical industrial hygiene samplers (e.g., respirable), nanoparticles have substantially greater biological reactivity, deposition in the respiratory tract, and mobility in the body after depositing. Thus, freshly produced nanoparticles near fume sources may drive much of the observed adverse health effects, and respirable sampling may be insufficient to assess metal-based exposure risks. We have recently developed a novel personal sampler-the nanoparticle respiratory dose (NRD) sampler-and an associated analytical method that is easy to use, is inexpensive to analyze, and integrates into current personal exposure sampling strategies that can streamline the multi-step process for assessing titanium dioxide nanoparticle exposures. The work outlined in this application will expand the applicability of the NRD sampler and associated analytical methods to dramatically improve exposure assessment of a broad range of metal-based nanoparticle exposures in the workplace. With successful completion of the work proposed here, there will be many benefits, including an innovative, new sampler (Aim 1) coupled with associated analytical methods (Aim 2) applicable to assessing exposures to airborne metal-based particles. These new methodologies, validated through field studies (Aim 3), will be available for exposure assessments in routine industrial hygiene practice and in epidemiological study to better elucidate the adverse health effects that may be associated specifically with certain metal-based nanoparticle exposures. Consequently, our methods will have widespread use to assess exposures in the burgeoning field of nanotechnology or in more traditional occupational settings such as where welding occurs.